Microscopic description:

Microscopic examination of the mass exhibited a large, mostly necrotic benign polypoid epithelial "polyp"/mass with prostatic type epithelium, with a cystic growth pattern. The neoplasm, including the necrotic areas, measured 9.2 cm in greatest dimension. The mass appeared to arise from the prostatic urothelium and into the bladder mucosa, with additional involvement of the right seminal vesicle area. Extensive acute and chronic inflammation of the bladder wall surrounding the necrotic areas was also noted. All margins were negative for cancer.

Immunohistochemical staining performed at The Ohio State University was positive for PSAP, PSA, NKX3.1, p63, CK903, and negative for GATA3, CK7, AMACR, and CK20. GATA3 and CK7 were only positive within the urothelial lining.

Discussion:

Prostatic-type epithelial polyps were first described approximately 100 years ago. Since then, such lesions have been uncommonly found within the urinary tract, often forming on the posterior urethra The minority of lesions found in the bladder are most located in the trigone. To the best of our knowledge, our case report is only the second featured within the literature to include involvement of the right lateral bladder wall.

In diagnostic evaluation of prostatic-type polypoid urothelial lesion, great consideration must be given to prostatic ductal adenocarcinoma. This vital differential for exclusion typically contains a comparatively enhanced architectural complexity of cribriform and anastomosing cords, pseudostratified columnar epithelium, and prominent nucleoli belying low-grade nuclear features. Immunohistochemical staining of prostatic ductal adenocarcinoma is similarly positive for PSA and PAP / PSAP

Other differential diagnosis to consider in evaluation of a prostatic-type lesion of the urothelium include urothelial carcinoma with glandular differentiation, papillary urothelial neoplasm, benign prostatic hyperplasia (BPH), nephrogenic adenoma, polypoid or papillary cystitis, cystitis cystica, and cystitis glandularis.

References:

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CASE IMAGES